A damped flywheel of this type is described in French published patent specifications FR 2 554 891A and FR 2 576 357A.
The support means usually consist of a rolling bearing such as a ball bearing, which substantially increases the selling price of the damped flywheel. This cost is particularly high due to the fact that this bearing has to be able to withstand temperatures of the order of 200.degree. C. In this connection, in a motor vehicle, one of the two coaxial masses in the flywheel comprises a plate which acts as the reaction plate of a clutch, and which can reach considerably temperatures during heavy use. In addition, the bearing is usually lubricated in such a way that the grease which it contains can tend to escape, thus contaminating the reaction plate and/or the friction device which is usually incorporated as part of the torsion damping device. All of this impairs both the performance and the useful life of the damped flywheel. A further disadvantage is that the bearing is liable to seize up.
In order to overcome the above mentioned drawbacks, it may be thought possible to use smooth bearings as described in the above mentioned patent specifications. However, other problems also arise in a damped flywheel, and in particular problems connected with the lubrication of smooth bearings, as well as those of resistance to abrasion (due to the oscillating motions of the damped flywheel), and problems of the temperature and thickness of the bearing.
In addition, corrosion problems can occur, especially when the vehicle is immobilised for a long time. All of this has led to the fact that smooth bearings have not so far found any favour for use in damped flywheels.
In addition to the foregoing, it is desirable that the support means should have a coefficient of friction as small as possible.